1. Field of the Invention
This invention relates to the field of hand tools for the machinist industry. More particularly, this invention concerns a gripping device for holding gauge pins for use in determining when desired hole size has been achieved.
2. Description of the Prior Art
In drilling holes in metals and ceramics, high tolerances for exactness of hole size is critical. Short tubular pins called "gauge pins", machined to exact diameters, are sold to machinists and widely used throughout the industry for insertion into freshly drilled holes for determination as to whether the proper diameter has been achieved. The words "GO" and "NO GO" are industry nomenclature representing successful achievement of proper hole size and less than successful achievement respectively. Prior to achieving the proper sized hole, the maximum and minimum sized pins, corresponding to the maximum and minimum diameter or "call-out" in the blue prints, will not fit or "NO GO" in the hole. When the proper hole size has been achieved, the minimum size pin fits tightly or "GOES" in the hole.
Because of the tight fit between the gauge pin and the hole into which it is inserted, the pins cannot be inserted and withdrawn by hand. The pin is too smooth and is hard to hold; the fit develops substantial friction between the pin and the hole, too much for hand-holding of the pin. Furthermore, body oils and perspiration transferred from the machinist's hand to the pin alters the dimensional tolerance of the pin and is a source of potential corrosion of the metal making up the pin. For these reasons, gauge pins have traditionally been mounted in holders and the holders gripped with the hand for use.
Gauge pin holders are many and varied. They abound in all machine shops. They possess numerous disadvantages, however, that have marked them as a constant source of irritation to machinists. For instance, the most popular gauge pin holders comprise a two-halved, elongated handle with axial grooves set adjacent the ends for receipt of the gauge pins. The handles are joined by a threaded cross-bolt midway between the two ends, see U.S. Pat. No. 3,515,398. This holder suffers from a serious problem in that as the cross-bolt is tightened, the gauge pins at the ends generate torque about the cross-bolt that results in fractures in the handle.
Other problems are that the present gauge pin holders have to be hand-made and are rather expensive - see U.S. Pat. Nos. 1,980,087; 2,392,317; 2,582,679; 2,861,347; 3,023,015; 3,515,398; 3,754,767; 4,143,446 and French Pat. No. 80247. Many of them have centermounted clasping features that bend and fracture when tightened, see U.S. Pat. Nos. 560,821; 2,345,750; 2,582,679; 2,861,347 and 3,515,398. Many of them do not have full-width clamping thereby posing damage to the gauge pin from over-clamping in one particular spot, see U.S. Pat. Nos. 2,065,472; 2,392,317; 2,582,679; 2,861,347; 3,023,015 and 3,515,398. Other holders do not have a long enough handle to be easily usable, see U.S. Pat. Nos. 2,044,679 and 3,023,015. Some do not have separate adjustments for each pin to be held therein, see U.S. Pat. Nos. 560,821; 2,044,679; 2,582,679 and 4,343,446. Many holders have no ability to hold a variety of sizes or hold them all in one direction, see U.S. Pat. Nos. 1,980,087; 2,392,317; 4,143,446 and French Pat. No. 80247. Some holders do not mount the pins axial to the handle, see U.S. Pat. Nos. 1,980,087 and 2,903,797. Others cannot hold two distinct sizes of gauge pins without difficulty, see U.S. Pat. Nos. 560,821; 1,980,087; 2,044,679; 2,065,472; 2,582,679; 3,515,398; 4,143,446 and French 80247. Finally, many holders are not amenable to easy gauge pin changing, see U.S. Pat. Nos. 2,345,749; 2,345,750; 2,392,317; 2,861,347 and 4,143,446.